To more accurately simulate flood propagation in the Qinhuai River Basin, a loose coupling approach was employed to integrate hydrological processes with one-dimensional (1D) and two-dimensional (2D) hydrodynamic processes. A coupled distributed hydrological-hydrodynamic model was developed by combining the grid-Xin’anjiang model for upstream hydrological simulation with 1D and 2D hydrodynamic models to simulate downstream flow dynamics. Specifically, a 1D model was applied to river channels, while a 2D model was utilized to simulate flood inundation in complex urban environments. This study proposes a comprehensive distributed hydrological-hydrodynamic coupling model that effectively represents the entire basin’s behavior. The results demonstrate that the model effectively simulates five flood events from 2015 to 2020, achieving an average Nash-Sutcliffe Efficiency Coefficient of 0.932, indicating high accuracy and reliability. As a case study, the 20200713 flood event was analyzed, revealing critical flood risks in areas such as Zhenghuai Road, Fenghuang East Street, and the Wudingmen Sluice area with maximum inundation depths exceeding 0.5 meters.